Steel Fork straightneing
Just picked up this Fuso FRX #550 ... But... And it's a big one! The front fork is bent from a collision. The fork crown is fine. I just need to find a mechanic in the Tampa Bay Area willing to straighten it. I talked to Dave Moulton, the builder, and he says it can definitely be straightened. The shops I've talked to keep saying they can't due to liability issues. Help!
https://cimg2.ibsrv.net/gimg/bikefor...c789e4989d.jpg |
I have never found a shop willing to straighten a fork. Too much potential liability for too little money. My LBS doesn't even install tubular tires anymore. I talked to him about it, the increase in his insurance to cover doing tubulars was about 10X the income it would generate. So it was a pretty simple decision. So I adopted a D-I-Y solution.
Lots of DIY options have been discussed on this forum. I've straightened a lot of forks, but ONLY on my personal keeper bikes. My method is not as good as the one below. No interest in taking on this risk for others. And in no way am I recommend you straighten the fork. Its really one of those decisions only you can make. And be sure to inspect the main frame carefully. Typically I will find either slight rippling, or cracks in the paint on the DT and TT near the HT. https://www.bikeforums.net/bicycle-m...bent-fork.html |
Ship the fork to Dave Moulton?
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Try posting in the Framebuilders section as well. https://www.bikeforums.net/framebuilders/
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Considering the ramifications of a front fork failure, you might consider locating someone who definitely knows how to repair the fork (Dave's apprentice) than someone willing to do it.
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Get a long pipe, about a foot longer than the fork mask the fork so it doesn't get scratched, and go to town on it. You may have to take it to a bike shop to get the final alignment using a jig. But you can also just try riding it and if it ride straight with no hands, it's aligned.
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Originally Posted by San Rensho
(Post 21277004)
Get a long pipe, about a foot longer than the fork mask the fork so it doesn't get scratched, and go to town on it. You may have to take it to a bike shop to get the final alignment using a jig. But you can also just try riding it and if it ride straight with no hands, it's aligned.
So this is what I did with the help of a local frame builder. All straight & Aligned. Thanks to everyone, especially Dave Moulton, for the assistance. |
When we bent our forks jumping bikes, a junk wheel was installed, the fork turned around and wham! into the wall it went. This bent the fork blades back to straight (by sight, not measurement).
Another method is to install a dummy axle and use a lever against the crown to bend the blades in unison. Will need to measure for alignment either way. |
Originally Posted by LawsonMitchell
(Post 21277055)
So this is what I did with the help of a local frame builder. All straight & Aligned. Thanks to everyone, especially Dave Moulton, for the assistance.
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Ask me how I know.
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Originally Posted by LawsonMitchell
(Post 21277055)
All straight & Aligned.
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Dave is semi-retired
Originally Posted by dsbrantjr
(Post 21276631)
Ship the fork to Dave Moulton?
Dave Moulton's Blog - Dave Moulton's Bike Blog |
Originally Posted by San Rensho
(Post 21277735)
Ask me how I know.
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Originally Posted by Amt0571
(Post 21283718)
How do you know? :lol:
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San Rensho, you rode home from the race with your chin split open? One tough SOB.
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When metal gets bent, it's molecules of the material getting torn apart. Those ripped apart molecules are typically too small to see. When you try to straighten a fork, you aren't putting those torn molecules back together, you tearing more apart in the vicinity. You aren't unbending, you are bending again in hopes of countering the deformed geometry. Get it looking straight and you have approximately doubled the damage you had after the initial bend. Steel is perhaps the most forgiving material. Aluminum typically just snaps off when you try to unbend it. Heating to red hot can allow you to alter the shape but it need proper annealing to regain some of the strength. On a bike like this one, the heat required would melt the brass in the crown.
Some times the steerer gets bent too. You never know what the weakest point of a bike is until it gets crashed. Sometimes the wheel fails, sometimes the frame gets bent, sometimes it's the steerer or blades. Rarely all are of equal strength. I've seen frames ripped apart in collisions where the fork and wheel were okay. Look for cracks or ripples in the paint just behind the head tube. That's a sign the frame got damaged too. |
Originally Posted by rickpaulos
(Post 21287144)
When metal gets bent, it's molecules of the material getting torn apart. Those ripped apart molecules are typically too small to see. When you try to straighten a fork, you aren't putting those torn molecules back together, you tearing more apart in the vicinity. You aren't unbending, you are bending again in hopes of countering the deformed geometry. Get it looking straight and you have approximately doubled the damage you had after the initial bend.
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So now I have to sleep with the guilt of tearing molecules apart? Andy
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